Colorimetric oxygen detectors

ABSTRACT

An oxygen detector which undergoes a color change to indicate the presence of oxygen and certain oxygen-containing compounds in a gas stream in which the oxygen or the oxygen-containing compound can be present in a concentration of less than 1 parts per million which comprises a supported oxide of a metal of group VB or VIB of the periodic table, the metal being in a lower valence state.

United States Patent Cagle et al. 1 May 16, 1972 541 COLORIMETRIC OXYGEN2,959,578 11/1960 Hogan .1252/458 x DETECTORS OTHER PUBLICATIONS 72Inventors: Glen E. Ca e' Donald R. Witt both of l Bartlesvme Mellor,Comprehensive Treatise on Inorganic and Theoretical 1 Chemistry, Vol. 9,pp. 744, 754 (1929). 1 Asslsneei Phillips Petroleum p y Mellor, v01.11,pp. 177, 178,207 1931 [22] Filed: July 24 1969 Bennett, ConciseChemical and Technical Dictionary, pp.

216,968(1947). [21] Appl. No.: 844,637

Primary Examiner-Joseph Scovronek 52 us. c1. ..23/232 R, 23/2 5, 23/254R, and Qulgg 252/458 51 1111.01. ..G0ln 21/16 1 ABSTRACT [58] Field ofSearch ..23/232, 254, 2 S, 230 M An oxygen deecmr which undergoes achange to dicate the presence of oxygen and certain oxygen-containing[56] References Cmd compounds in a gas stream in which the oxygen or theoxygen- UNITED STATES PATENTS containing compound can be present in aconcentration of less than 1 parts per million which comprises asupported oxide of 3,340,014 9/1967 Neal et al ..23/254 3 metal f groupVB or f the periodic table, the meta] Rama ....23/2 S being in a lowervalence tate 3,535,074 10/1970 Nakashima.. ....23/2 S 3,361,531 1/1968Erb et a1. ..23/25 X 8 Claims, No Drawings COLORIMETRIC OXYGEN DETECTORSThis invention relates to colorimetric detectors.

In one of its more specific aspects, this invention relates to detectingmaterials which undergo color change to indicate the presence of anextraneous material.

The use of materials which undergo color change for detection of thepresence of an extraneous material is well known. Such materials areparticularly valuable when they are employable for the purpose ofremoving those components to which they are sensitive from gas streamsin which the extraneous gas is present in minute quantities. Suchmaterials are additionally valuable if the extent of their color changecan be employed to determine the quantity of the extraneous material inthe gas stream.

This invention provides such materials and the methods for theirproduction and use.

According to the method of this invention, there is provided a processfor detecting the presence of oxygen in a gaseous stream which comprisescontacting said stream with a composition comprising a supported oxideof a metal of group VB or VIB of the periodic table [Handbook ofChemistry and Physics, Chemical Rubber Co., 45th Edition (1964), p. 8-2]in a lower valence state to effect a color change in the composition.

The oxygen may be present as molecular oxygen or as oxygen in the formof sulfur and nitrogen oxides such as S N 0 and N0 Accordingly, it is anobject of this invention to provide materials suitable for removal ofminute traces of components from gaseous streams.

It is another object of this invention to provide agents for thequantitative measurement of components contained in gaseous streams inminute quantities.

This invention contemplates use of a salt or mixture of salts of themetals of groups VB or VlB in the preparation of the detectors. Thesemetals include vanadium, niobium, tantalum, chromium, molybdenum, andtungsten. Preferably, the applicable compounds of these metals are thehalides, sulfates, nitrates, oxides, oxyhalides, oxysulfates andphosphates. Preferred compounds for use in nonaqueous solvents areorganometallic compounds such as those recited in the Handbook ofChemistry and Physics, Chemical Rubber Company, 48th edition(1967-1968), pp. C-650 through C-685. Particularly preferred compoundsare the carbonyl compounds and the bis-cyclopentadienyl compounds. Thecompounds used are at least slightly soluble in an aqueous or nonaqueousmedium in order to facilitate their deposition on the support.

Preferred supports are silica-containing supports such as silicas andsilica-aluminas although the nature of the support is not of primaryimportance. To facilitate the usage in the conventional manner, thesupport is preferably particulate.

A group VB or VlB metal compound is deposited on the particulate supportfrom a solution chosen in consideration of the solubility of the metalcompound therein. For example, suitable nonaqueous solvents arearomatics, esters, ketones, paraffins, cycloparaffins, and the like. Anyaqueous or nonaqueous solution is satisfactory which deposits the metalcompound on the support to give a concentration of metal in the range offrom about 0.01 to about 10 weight per cent, preferably from about 0.lto about 5 weight per cent of the weight of the combined support andcompound. The feasible concentration is largelydependent upon theconcentration of the gas to be detected in the gaseous stream. Predryingof the support is desirable when a nonaqueous solution of the metalcompound is used, but it is not necessary when an aqueous per volume ofparticulate solid. However, these ranges are only the most practicalinasmuch as given enough time, almost any space velocities can beemployed.

if hydrogen is employed to reduce the detector, the detector can beemployed in detecting oxygen in gas streams which contain olefins,inasmuch as the detector will not act to polymerize the olefins.However, if carbon monoxide is employed to reduce the detector, thereduced detector, when employed for the detection of oxygen in olefinstreams, will tend to polymerize the olefins. For this reason, detectorsintended for determination of oxygen in olefin streams and which havebeen reduced by carbon monoxide, will be contacted by flue gas, steam,or steam including inert diluents in order to inactivate the detector inrespect to polymerizing olefins. Such inactivation is necessary onlywhen the detector is to be contacted in use by a stream containingolefins.

This procedure forms a supported oxide compound which is capable ofexisting in two oxide states of different valences and of perceptiblydifferent colors, the compound undergoing a change in color upon contactwith oxygen, or oxygen-containing compounds, at ambient temperatures.

The following examples will illustrate the invention.

About 0.75 part by weight of VOSO, was dissolved in about 42 parts byweight of deionized water. About 9.4 parts by weight on a dry basis offinely-divided silica are added to the solution and the resultingmixture was evaporated to dryness and the residue was dried at 1,000 F.for 2 hours. The dried residue was light yellow.

The dried residue was reduced for about 30 minutes at 1,000 F. in astream of carbon monoxide and then flushed with nitrogen for about 40minutes. The reduced detector was violet in color. A portion of thisdetector was placed in a glass tube having a diameter of 8 mm. and flowof a nitrogen stream containing about 1 part per million oxygen wasrouted therethrough. The detecting compound underwent a change in colorfrom violet to light yellow, there being a column 2.0 mm. in lengthchanging color for each 10 cubic feet of gas passed across the detector.Regeneration of the detector to its reduced form in the mannerpreviously described was accomplished thereafter, after which reuse ofthe detector was possible.

In another instance, a finely-divided silica support having thereon 1.3weight per cent CrO deposited from aqueous solution by theaforementioned procedure was dried for about 5 hours at l,400 F. afterwhich it was reduced by contacting with carbon monoxide at 750 F. for 30minutes. The reduced material was flushed with nitrogen and possessed ablue color. Two quantities of the reduced material were placed inseparate glass tubes, each tube having a diameter of 8 mm. Each quantityof the reduced material was then contacted with a nitrogen streamcontaining oxygen in the amount of 9 parts per million. Under theseconditions, a zone of the detecting material was altered in color fromblue to yellow, the rate of interface travel between the two color zonesbeing 1.04 mm. per part per million of oxygen. Similarly, quantities ofthis material were contacted with a nitrogen stream containing 33 partsper million of oxygen. In this instance, a zone of the detector materialagain underwent a change in color from blue to yellow. The rate ofinterface travel between the two zones in this instance was 1.08 mm. perpart per million oxygen.

In both instances the detector was regenerable, undergoing a reversecolor change, upon reduction and upon retesting indicated a comparablerate of interface travel between color zones.

For detection of N 0, N0 and 50;, the preparation of the detectingcompounds and their reduction are as previously recited. In thisinstance, CrO on silica, reduced in carbon monoxide to a blue coloredmaterial, underwent the following changes in color in detecting thematerials indicated:

NO blue to orange-brown to orange N Oblue to orange SO blue to green Theabove data indicate the preparation of a suitable oxygen determiningagent from group VB and VlBmetals and the use of such agents to detectand to analyze for oxygen and oxygen-containing gases in gases in whichthey are present in minute quantities.

Certain modifications will be evident from the above discussion. Suchhowever, are considered to be within the skill of the art.

What is claimed is:

1. A method for determining the presence of oxygen in anolefin-containing stream in the absence of substantial polymerization ofthe olefin, said oxygen being present in said stream in the form ofmolecular oxygen, 80,, N and N0 which method comprises contacting saidstream at ambient temperatures with a colorimetric oxygen detectorcomposition comprising a supported metal oxide which undergoes a colorchange upon contact with said olefin-containing stream, said colorchange being quantitatively related to the quantity of oxygen present insaid stream, said colorimetric oxygen detector composition having beenprepared by:

a. impregnating a particulate silica-containing support with a solutioncomprising a compound of a metal selected from the group consisting ofchromium, molybdenum, tungsten, niobium, and tantalum in an amountsufficient to deposit 0.01 to about weight percent of said metal on saidsupport;

b. calcining the impregnated support by heating in the presence of airto convert said compound to an oxide of said metal; and

c. reducing the metal oxide obtained in (b) by contacting with hydrogento produce said colorimetric oxygen detector composition, at least aportion of said metal being in a lower valence state so that saiddetector undergoes a color change upon contact with oxygen or saidoxygencontaining compounds.

2. The method of claim 1 in which said metal is chromium and saidcompound of said metal is at least one selected from the groupconsisting of halides, sulfates, nitrates, oxides, oxyhalides,oxysulphates, phosphates, carbonyls and biscyclopentadienyls.

3. The method of claim 1 in which said hydrogen is passed into contactwith said oxide at a space velocity within the range of from about 100to about 10,000 volumes of hydrogen per volume of said support.

4. The method of claim 1 in which said solution comprises CrO in waterand in which said support is particulate silica.

5. A method for determining the presence of oxygen in anolefin-containing stream in the absence of substantial polymerization ofthe olefin, said oxygen being present in said stream in the form ofmolecular oxygen, 80,, N 0 and NO which comprises contacting said streamat ambient temperatures with a colorimetric oxygen detector compositioncomprising a supported metal oxide which undergoes a color change uponcontact with said olefin-containing stream, said color change beingquantitatively related to the quantity of oxygen present in said stream,said colorimetric oxygen detector composition having been prepared by:

a. impregnating a particulate silica-containing support with a solutioncomprising a compound of a metal selected from the group consisting ofchromium, molybdenum, tungsten, niobium, and tantalum in an amountsufficient to deposit 0.01 to about 10 weight percent of said metal onsaid support;

b. calcining the impregnated support by heating in the presence of airto convert said compound to an oxide of said metal;

c. reducing the metal oxide obtained in (b) by contacting with carbonmonoxide, at least a portion of said metal being in a lower valencestate so that said detector undergoes a color change upon contact withoxygen or said oxygen-containing compound; and

d. contacting the carbon monoxide reduced metal oxide formed in step (c)with a gas selected from the group cons1st1ng of flue gas, steam andnitrogen to inactivate said metal oxide for the polymerization ofolefins and produce said colorimetric oxygen detector composition.

6. The method of claim 5 in which said metal is chromium and saidcompound of said metal is at least one selected from the groupconsisting of halides, sulfates, nitrates, oxides, oxyhalides,oxysulphates, phosphates, carbonyls and biscyclopentadienyls.

7. The method of claim 5 in which said carbon monoxide is passed intocontact with said oxide at a space velocity within the range of fromabout to about 10,000 volumes of hydrogen per volume of said support.

8. The method of claim 5 in which said solution comprises CrO in whichsaid support is particulate silica.

2. The method of claim 1 in which said metal is chromium and saidcompound of said metal is at least one selected from the groupconsisting of halides, sulfates, nitrates, oxides, oxyhalides,oxysulphates, phosphates, carbonyls and bis-cyclopentadienyls.
 3. Themethod of claim 1 in which said hydrogen is passed intO contact withsaid oxide at a space velocity within the range of from about 100 toabout 10,000 volumes of hydrogen per volume of said support.
 4. Themethod of claim 1 in which said solution comprises CrO3 in water and inwhich said support is particulate silica.
 5. A method for determiningthe presence of oxygen in an olefin-containing stream in the absence ofsubstantial polymerization of the olefin, said oxygen being present insaid stream in the form of molecular oxygen, SO2, N2O and NO2, whichcomprises contacting said stream at ambient temperatures with acolorimetric oxygen detector composition comprising a supported metaloxide which undergoes a color change upon contact with saidolefin-containing stream, said color change being quantitatively relatedto the quantity of oxygen present in said stream, said colorimetricoxygen detector composition having been prepared by: a. impregnating aparticulate silica-containing support with a solution comprising acompound of a metal selected from the group consisting of chromium,molybdenum, tungsten, niobium, and tantalum in an amount sufficient todeposit 0.01 to about 10 weight percent of said metal on said support;b. calcining the impregnated support by heating in the presence of airto convert said compound to an oxide of said metal; c. reducing themetal oxide obtained in (b) by contacting with carbon monoxide, at leasta portion of said metal being in a lower valence state so that saiddetector undergoes a color change upon contact with oxygen or saidoxygen-containing compound; and d. contacting the carbon monoxidereduced metal oxide formed in step (c) with a gas selected from thegroup consisting of flue gas, steam and nitrogen to inactivate saidmetal oxide for the polymerization of olefins and produce saidcolorimetric oxygen detector composition.
 6. The method of claim 5 inwhich said metal is chromium and said compound of said metal is at leastone selected from the group consisting of halides, sulfates, nitrates,oxides, oxyhalides, oxysulphates, phosphates, carbonyls andbis-cyclopentadienyls.
 7. The method of claim 5 in which said carbonmonoxide is passed into contact with said oxide at a space velocitywithin the range of from about 100 to about 10,000 volumes of hydrogenper volume of said support.
 8. The method of claim 5 in which saidsolution comprises CrO3 in which said support is particulate silica.